1. Field of the Invention
The present invention relates to an apparatus for ironing and doming drawn cup-shaped blanks into drawn and ironed can bodies and, more particularly, to an ironing and doming apparatus provided with a mechanism for feeding the cup-shaped blanks successively to their working positions.
2. Description of the Prior Art
Conventionally, drawn and ironed can bodies are most commonly made, for example, by blanking and drawing a metal strip into cup-shaped blanks with a press and then redrawing and ironing the drawn cups into the can bodies by another presses in a manufacturing line. In these redrawing and ironing processes on a press, the cup-shaped blanks are pushed, one at a time, through redrawing and ironing dies and against a domer by a punch attached to a reciprocating ram and formed into such can bodies with domed bottoms all by a single stroke of the ram. Apparatuses for these ironing and doming processes are disclosed in Japanese Patent Publication No. 39516/1975, Japanese Patent Application Publication No. 184429/1985, and U.S. Pat. No. 3,446,167.
The apparatuses, as disclosed in Japanese Patent Publication No. 39516/1975 and Japanese Patent Application Publication No. 184429/1985, are so-called horizontal type ironers each having a punch mounted to an end of a horizontal ram driven back and forth by a drive means such as a crank mechanism. Provided on the way of the forward stroke of the punch and coaxially aligned therewith are a redrawing die and a number of ironing dies each having a slightly different internal diameter from one another and being arranged in the order of gradually reducing internal diameters. A stripper for stripping a shaped can body from the punch is arranged behind the last of the ironing dies. With each of these ironers, the cup-shaped blanks are placed one at a time in front of the punch in a retracted position. By moving the punch forward in this state, a cup-shaped blank placed as above is pushed at first into the redrawing die and then through the ironing dies and formed into an ironed can body. The ironed can body thus formed is stripped from the punch by the stripper on the way of a backward stroke of the punch, so that the stripped can body drops into a predetermined position and discharged.
U.S. Pat. No. 3,446,167, on the other hand, discloses a vertical type apparatus having ironing dies and domers acting as bottom shaping members both held around the arms of a rotary turret member. At the same time, punches are attached to carriers which rotate together with the rotary turret member, such that those punches are movable upward and downward relative to those ironing dies and domers. While cup-shaped blanks fed to above the ironing dies are moving together with the rotary turret member, the punches are moved downward to effect the ironing and doming processes and the shaped can bodies are taken out at discharge positions.
In the forming of drawn and ironed can bodies by the horizontal type apparatuses, the cup-shaped blank is pushed through the ironing dies and against the domer by the leading end portion of the punch, so that the punch is essentially held at its trailing end portion in the so-called "cantilever manner" by the horizontal ram. In the aforementioned horizontal type ironing and doming apparatus, therefore, the punch tends to be slightly deflected downwardly at its leading end portion by its own gravity, occasionally causing uneven thickness distribution of the ironed sidewall of the shaped can body. In order to eliminate this disadvantage, the above mentioned Japanese Patent Application Publication No. 184429/1085 discloses the unique means of tilting the ironing dies. However, such means is too sophisticated to be readily put into practical use commercially. Moreover, it is practically very difficult to design and build a horizontal type ironer having a plurality of reciprocating punches as such punches can not readily be maintained in accurate parallel relationship with each other due to the aforementioned deflections. This has been making it inevitable to provide a conventional horizontal type ironer with only one punch, one set of ironing dies and one domer. In other words, such ironer can produce only a single can body per stroke, and a number of units of such ironer have to be installed at significantly high equipment costs to achieve adequate commercial production.
In the aforementioned vertical type apparatus, the above mentioned deflections of the punches are eliminated as the punches are subjected to own gravity in their axial direction. On the other hand, however, it is extremely difficult to align the individual punches respectively with a large number of ironing dies mounted on the rotary turret member as the punches are attached to the carriers rotatably provided at the upper portions of the apparatus to rotate together with the rotary turret member and such punches are guided by guide arms and cam operated to move up and down respectively. Therefore, such apparatus essentially requires a disadvantageously complicated mechanism. Even if appropriate alignment of the punch and the dies could be accomplished, such apparatus is essentially subjected to highly localized dynamic loads concentrating on its circumference where the rotating dies move, and thus, such circumferential portions of the frame of the apparatus will have to be made rigid enough to withstand the highly localized dynamic loads to ensure operating accuracy. In any event, the aforementioned vertical apparatus having the rotary turret member has to be complicated in the construction and sizable, so that it can not readily be put into practical use or operated efficiently.
In the ironing process to manufacture drawn and ironed can bodies as so far described, cup-shaped blanks are successively conveyed to processing positions. For this purpose, U.S. Pat. No. 3,446,167 discloses a feeder comprising: a screw conveyor having spiral grooves for advancing the cup-shaped blanks; a star wheel having recesses for receiving the cup-shaped blanks from the screw conveyor; and guide members for guiding the cup-shaped blanks. In this feeder, rotations of the star wheel move the cup-shaped blanks in the recesses along the guide into predetermined positions over the ironing dies or ironing rings. Since this feeder disclosed in U.S. Pat. No. 3,446,167 has only one outlet for the supply to a plurality of the ironing rings the feeder has to move the cups at accelerated speed and stable supply of the cups cannot be ensured at all times. Also, since the cups are transferred from the screw conveyor to the star wheel and then from the star wheel to the ironing rings, a relatively complicated and sizable drive mechanism is required to operate such feeder, and therefore, it is not possible to arrange a plurality of units of such feeder closely adjacent to one another.
On the other hand, a device for supplying a horizontal type ironer with cup-shaped blanks is disclosed in Japanese Utility Model Publication No. 23076/1985. This feeding device comprises: an L-shaped guide frame for stacking a plurality of cups one above another with their axes positioned horizontally and guiding the cups at the bottom of the guide horizontally in a direction perpendicular to their axes; and a push plate disposed at the lower end corner of the guide frame and adapted to move rockingly on an axis parallel with the axes of the cups to urge the cups along the bottom of the guide horizontally and bring them one at a time into coaxial alignment with the punch. However, this device has a disadvantage in that the feed speed is essentially limited as excessively vigorous rocking movements of the push plate will give undesirably large inertial force to the cups. Also, this feeding device is applicable only to a horizontal type ironer.